1-3 Segments and Their Measures

Allie Snider

Summary:

This section will teach you how to measure line segments. One way to measure segments is using the Distance Formula. This section is in the textbook from pages 17-23.

Vocabulary for this section:

Postulates- rules in math that you don't have to prove; they are just accepted
Theorems- rules in math that have to be proven
Between- refers to 3 collinear points. One of the points is "between" the other two
Congruent Segments- line segments whose lengths are the same

Postulates/Theorems:

  • Ruler Postulate- states that points on a line can be substituted with real numbers. That real number is called the coordinate of that point.


(The name of a point can be point A but the coordinate of it can be X1)

The distance between J and K is the absolute value of the difference of coordinates J and K.

  • Segment Addition Postulate- 2 parts of a line segment equal the entire segment.


snider_seg_add_post.png
  • Pythagorean Theorem


snider_pythag._thm.png


The Distance Formula:


Picture_1.png


SAMPLE PROBLEMS:

Find the distance between each set of points. S(0,6) T(8,12)
1)
Picture_10.png
















2) A(1,-2) B(-2,-6)


Picture_6.png


Draw a sketch of the 3 collinear points. Then, write the Segment Addition Postulate for the points
3) W is between A and F

Picture_fejkgh.png





AW+WF=AF

PRACTICE PROBLEMS:

Use the Distance Formula to decide whether JK is congruent to KL.
1) J(0,-8)
K(4,3)
L(-2,-7)

Suppose M is between L and N. Use the Segment Addition Postulate to solve for the variable. Then, find the lengths of LM, MN, and LN.
2) LM= 7y+9
MN= 3y+4
LN= 143

Find the distance between the 2 points.
3) B(7, -5) D(3,0)

4) R(-12, 8) K(-7, 1)



http://www.purplemath.com/modules/distform.htm

http://www.algebra.com/algebra/homework/Length-and-distance/Length-and-distance.faq.question.152614.html